This invention relates to a spin-stabilized projectile having a guide band of predetermined length frictionally and/or form-fittingly connected to the projectile body. The invention also relates to a method of making such a spin-stabilized projectile.
In spin-stabilized projectiles the projectiles have guide bands for transferring the torque to the projectile from the rifling of the weapon barrel. The guide bands are frequently made of copper or a copper alloy. The guide bands have such a diameter that as the projectile passes through the barrel, they are pressed into the rifling thereof.
Copper guide bands have the disadvantage that particularly in case of large-caliber weapon systems having barrels of substantial length, the flanks of the guide bands are exposed to an increased wear. Such a guide band wear leads to problems in imparting twist (torque) to the projectile. Further, the sealing of the guide band against the hot propellant gases is no longer securely provided as the projectile passes through the barrel.
It is known to replace copper as the guide band material with soft iron to reduce the guide band wear. Soft iron guide bands, however, have the drawback that the weapon barrel wear is significantly greater than in case of copper guide bands.
Further, German Patent No. 308,537 discloses a spin-stabilized projectile whose guide band is composed of two partial guide bands arranged in series as viewed along the longitudinal axis of the projectile. The first partial guide band which is closer to the rearward terminus of the projectile is made of soft iron and extends over the preponderant length portion of the guide band. The second partial guide band is an axially narrow annulus made of copper or another soft metal. As the guide band penetrates into the weapon rifling, the copper ring causes a thin copper coating to be deposited on the partial, soft iron guide band. Thus, the copper ring functions as a lubricant and therefore counteracts a premature wear of the weapon barrel.
It is a disadvantage of the above-discussed known projectiles having two-part guide bands that particularly upon firing of large caliber projectiles from long weapon barrels, the weapon barrel is nevertheless frequently damaged because of the relatively long partial, soft iron guide band.
It is an object of the invention to provide a spin-stabilized projectile and a method of making the same, wherein the barrel wear is comparable to that caused by conventional guide bands made of a copper based alloy.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the spin-stabilized projectile has a projectile body and a guide band being circumferentially mounted on an outer face of the projectile body. The guide band includes a plurality of axially adjoining partial guide bands. One of the partial guide bands is a first partial guide band made of copper, a copper alloy or another soft metal. One of the partial guide bands is a second partial guide band made of soft iron and axially adjoining the first partial guide band. A total axial length of all second partial guide bands is between 5% and 50% of the total axial length of the guide band.
The invention is essentially based on the principle to select the length of the partial guide band made of soft iron possibly short while ensuring that the soft iron guide band securely takes up the radial forces during stress. Tests have surprisingly shown that it is sufficient if the length of the partial soft iron guide band is between 5 and 50% of the length of the entire guide band.
When using 155 mm caliber ammunition fired from weapon barrels having a 52-caliber length, a length of the partial soft iron guide band was found to be sufficient if it is between 20 to 40% of the axial length of the entire guide band.
According to an advantageous embodiment of the invention, the guide band is composed of at least four partial guide bands which are, as viewed axially, alternatingly of soft iron and copper (or a copper alloy) or of another soft metal. Again, the entire length of the soft iron partial guide bands is less than 50% of the length of the entire guide band.
In guide bands which have on their exterior surface grooves for relieving stress of material, it has been found advantageous to provide that the borders of adjoining guide band regions are situated between such grooves.
In the manufacture of the projectiles the partial guide bands are expediently first connected to one another by bonding such as gluing or welding and are only thereafter inserted on and secured to the projectile body.
In a further variant, the axially juxtapositioned guide bands may be mounted in a simple manner on the projectile body.
It has been found to be particularly advantageous to soft-solder or press a low melting point material such as zinc into one or several circumferential grooves of the partial guide band or bands.